Are you one of those parents who goes a little crazy watching your kids play sports? Crazy bad? As in attacking the referee or the opposing team. Well with baseball season on the way, we're going to... See More
Are you one of those parents who goes a little crazy watching your kids play sports? Crazy bad? As in attacking the referee or the opposing team. Well with baseball season on the way, we're going to see unfortunately a lot more of that, hopefully but not more. A mother threatening murder over little league. Here's Deborah Roberts. Reporter: It's springtime and that means little league sports. All about team building, right? Well, not exactly. Lately, it's a spectacle that seems to be on instant replay. Nearly every weekend perceived bad calls, leading to bad behavior. But it's not kid athletes who belong in the penalty box -- it's their parents. Fists. Four-letter words. Free-for-all brawls police he just got slam dunked! And what about this out-of-control dad? So fearful his son is losing a wrestling match he shoves a 10-year-old clear across the ring, really? But the mvp, most vicious parent award, may very well go to Janet chiauzzi. She may look like an unassuming suburban stay-at-home mom, but for more than a year she secretly terrorized her Long Island, New York, neighbors. We spent days, months, years, looking over our back. Reporter: It all began one summer. John Demasi was coaching his son Dominic's baseball team when an angry letter was sent to the league board claiming Demasi was playing favorites. It was just anonymous letter sent how wrong I was coaching the team and how bad we were. Reporter: Then there's another letter and another letter -- who could be so spiteful? Month after month, the letters kept coming. The demasis were scared for their lives. "I know where your wife goes every day. I know where your daughter goes to dance school." Reporter: How much did you alter your lives? I was working and I stopped. I didn't feel safe with, you know, somebody else driving my children. I just, I was afraid. There was times I slept out here - just nervous about who's coming to the door, who's passing by, and it wasn't easy. Reporter: But they found comfort in the friends, including Janet chiauzzi, a neighbor whose son played ball with Dominic and is in the same school. She suddenly began cozying up to Linda. Janet was texting me every other day. Reporter: Texting you about what? Anything. "Which nail salon do you go to?" Reporter: Even showing up at Linda's 40th birthday -- uninvited. And here at another event. Then, weeks later, a special delivery to the demasis. And there was two handwritten envelopes in our mailbox. So, I opened both of them. One was addressed to my son and one was addressed to me. "I made it my life's goal now to observe your family on a 24/7 basis. Don't be planning a vacation any time soon. You will have no home to come back to." Reporter: That had to knock you for a loop. I read the letter written to my son, which was just -- took me down, because it just said that if your father doesn't step back, I'm going to kill him. "You might never see your dad again. You all better watching your Backs. This is no joke. This is as real as it gets." "Get the hell out of east meadow baseball." That's to a ten-year-old child. Reporter: Could you believe that this is stemming from little league baseball? A death threat? No, I couldn't. But it did. Batten down the hatches, lock up, call the police. This is at a next level. Reporter: How frightened were your children? We sat him down and explained it. His initial reaction was to put down his glove and his bat and said, "You know what, dad? I don't need to play baseball anymore." Reporter: Yet, the demasis refused to give into their tormentor's demands. John remained the coach, a terrified Dominic still on the team. I was definitely nervous. And when I got up to bat, it felt like someone was always watching me. It definitely made the game more nerve-wrecking and harder to deal with. Reporter: As the frightened family struggled to go on, Nassau county police were sifting through the baseball parent list, looking for anyone who had an axe to grind. And they gradually began focusing on one key piece of evidence -- those envelopes that contained the hateful letters. If you just look at the town and the zip code on every single envelope, you can see that they're all the same handwriting. Reporter: And another slip up, the stamps were all identical. That made it apparent that we were dealing with the same person on each occasion. Reporter: But who? Turns out investigators were zeroing in on a parent no one would suspect -- that new friend Janet chiauzzi. Some of the content in the letters showed that this person had some intimate knowledge of the family's background and that's what ultimately led us to Ms. Chiauzzi. Reporter: But to nail her, police needed a copy of her signature. So, Linda Demasi hatches a plot to trick chiauzzi into giving her one. Linda has her 7-year-old daughter collect addresses for a fake fund-raiser. Chiauzzi takes the bait. The way she wrote "East meadow," it was a certain way. I could feel my knees starting to shake as I was standing there, and I couldn't believe it. Reporter: A chilling discovery. Linda knows beyond a doubt that her so-called good friend was harboring some bad blood. So suddenly you knew that Janet chiauzzi was part of this, was behind it. It was like a wave just came over us. Reporter: 48 hours later, police matched the samples. They had their woman. New this half hour a long Island mother arrested, accused of bad behavior. Reporter: Janet chiauzzi was arrested, charged with stalking the Demasi family. And she made a full admission to her authoring all the letters and making these malicious accusations. Reporter: But what could lead a parent to threaten to kill another? Chiauzzi told police she was angry because John, as coach, didn't choose her son for the little league travel team. Chiauzzi pled guilty and was sentenced to 60 days in jail, and ordered to stay away from Dominic Demasi. In a statement, her attorney says his client "Was genuinely remorseful and recognized the seriousness of her crimes." For the demasis, justice. But what they didn't get was an apology. I wish that, as a mother, she could look at me and say "I'm sorry. I'm sorry I did this."
This transcript has been automatically generated and may not be 100% accurate.